Onaka Lab Meeting¶

Discussion of Perrott et al. (accepted):¶

AMI-CL J0300+2613: a Galactic anomalous-microwave-emission ring masquerading as a galaxy cluster¶

Thursday, October 4th, 2017
Aaron Bell

Outline:¶

  • What is the AMI?
  • What is Sunyaev Zeldovich?
  • What did this paper find?
  • Open questions?

What is the Sunyaev-Zel'dovich effect?¶

"when CMB photons inverse-Compton scattered by hot plasma in a galaxy cluster's potential well"
-Shimwell et al. (2013)

  • Galaxy clusters can be traced by CMB fluctuations!
  • SZ causes a drop in flux at freq. < 217 GHz

What is AMI?¶

  • Arcminute Microkelvin Imager:

    "blind galaxy cluster survey [...] aiming to detect via the Sunyaev-Zel'dovich effect"
    -page 1

  • New digital correlator
  • Large-array: Sensitivity and resolution - foreground/background isolation
  • Small array: High surface brightness sensitivity - SZ imaging #### Small Array: #### Large array
  • 1972: Sunyaev & Zel'dovich claim CMB deviations can identify galaxy clusters
  • 2008-2011: AMI observes "blindly" at 15.7 GHz - detects several clusters
  • 2013: Schiwell+ report detection of "extended and unusual cluster" J0300+2613 via SZ
  • 2011-present: Anomalous microwave emission/spinning dust annoys cosmologists
  • 2015: AKARI Far IR data relased
  • 2017: Perrott+ claim J0300+2613 is just galactic dust! (not SZ, but AME)

What was their strategy?¶

  1. Repeat observation with new correlator
  2. Compare with newly available IR and MW data (i.e. AKARI!)
  3. Rule-out synchrotron with GLEAM 200 MHz data
  4. Rule-out free-free with GB6 5 GHz data
  5. Rule-out thermal dust emission via blackbody fit

Repeat J003+2613 observation with new correlator¶

Left: Analog Correlator¶
Right: Digital Correlator¶

DrawingDrawing

Compare to IR data:¶

Left: AKARI 140 micron¶
Center: AKARI 90 micron¶
Right: WISE 12 micron¶

DrawingDrawingDrawing

Rule out synchrotron with GLEAM 200 MHz:¶

Rule out free-free with GB6 5 GHz:¶

What did this paper find?¶

  • J0300+2613 correlates with IR emission
  • Obsvervation with upgraded instrument shows much weaker SZ-effect
  • Unlikely to be synchrotron or free-free emission

Open Questions¶

  1. What does J0300+2613 look like in MIR data?
  2. Could other SZ "clusters" be mislabled?
  3. Even if J0300+2613 is really Galactic emission-Is it necessarily AME?
    • What about free-free?
    • Synchrotron?
    • Thermal dust?

What does J0300+2613 look like in MIR data?¶

  • We can find out:
In [8]:
#Load `J0300+2613` coordinates into python:
from astropy.coordinates import SkyCoord # Low-level frames
import astropy.units as u
coord = SkyCoord('3:00:08.9','+26:16:29.1',frame='icrs', unit=(u.hourangle, u.deg))
#Convert to degrees RA DEC:
coord
Out[8]:
<SkyCoord (ICRS): (ra, dec) in deg
    ( 45.03708333,  26.27475)>
In [10]:
#So the kernel doesn't crash when we plot stuff in a notebook
%matplotlib inline 

# Convenient package for plotting FITS images
import aplpy 

def fits_display(image_file):
   
    # Create a new figure
    fig = aplpy.FITSFigure(image_file)

    # Show the colorscale
    fig.show_colorscale()

    # Make ticks white
    fig.ticks.set_color('white')

    # Make labels smaller
    fig.tick_labels.set_font(size=15)
    
    # Round out those tick labels:
    fig.tick_labels.set_xformat('ddd.dd')
    fig.tick_labels.set_yformat('ddd.dd')
    
    # Overlay a grid
    fig.add_grid()
    fig.grid.set_alpha(0.9)
    
    # Add a colorbar
    fig.add_colorbar()
    fig.colorbar.set_axis_label_text('Intensity (MJy/sr)')
    
    return fig

How the region looks if we make an exact cutout from raw IRC data:¶

Zodi is not subtracted!

In [18]:
# 9 micron data
fits_display('/home/aaronb/J003+2613/image/J003+2613_S.fits')
# 18 micron data
fits_display('/home/aaronb/J003+2613/image/J003+2613_L.fits')
WARNING: Cannot determine equinox. Assuming J2000. [aplpy.wcs_util]
WARNING:astropy:Cannot determine equinox. Assuming J2000.
WARNING: Cannot determine equinox. Assuming J2000. [aplpy.wcs_util]
WARNING:astropy:Cannot determine equinox. Assuming J2000.
INFO:astropy:Auto-setting vmin to  1.360e+01
INFO:astropy:Auto-setting vmax to  1.790e+01
INFO: Auto-setting vmin to  1.360e+01 [aplpy.core]
INFO: Auto-setting vmax to  1.790e+01 [aplpy.core]
Out[18]:
<aplpy.core.FITSFigure at 0x2ba51749ef50>
In [19]:
 
WARNING: Cannot determine equinox. Assuming J2000. [aplpy.wcs_util]
WARNING:astropy:Cannot determine equinox. Assuming J2000.
WARNING: Cannot determine equinox. Assuming J2000. [aplpy.wcs_util]
WARNING:astropy:Cannot determine equinox. Assuming J2000.
INFO:astropy:Auto-setting vmin to  1.360e+01
INFO:astropy:Auto-setting vmax to  1.790e+01
INFO: Auto-setting vmin to  1.360e+01 [aplpy.core]
INFO: Auto-setting vmax to  1.790e+01 [aplpy.core]
Out[19]:
<aplpy.core.FITSFigure at 0x2ba517d01a50>
In [17]:
# How the region looks in Zodi-subtracted All-sky Tiles
In [15]:
# 9 micron data:
fits_display('/work2/users/onaka/AKARI/IRC_AllSkyMap_2016/G156m27/G156m27_S_intensity.fits')
# 18 micron data:
fits_display('/work2/users/onaka/AKARI/IRC_AllSkyMap_2016/G156m27/G156m27_L_intensity.fits')
INFO:astropy:Auto-setting vmin to -5.674e+00
INFO:astropy:Auto-setting vmax to  7.043e+00
INFO: Auto-setting vmin to -5.674e+00 [aplpy.core]
INFO: Auto-setting vmax to  7.043e+00 [aplpy.core]
INFO
INFO:astropy:Auto-setting vmin to -9.226e+00
INFO:astropy:Auto-setting vmax to  9.921e+00
: Auto-setting vmin to -9.226e+00 [aplpy.core]
INFO: Auto-setting vmax to  9.921e+00 [aplpy.core]
Out[15]:
<aplpy.core.FITSFigure at 0x2b5323ee9750>
In [14]:
# 9 micron data:
fits_display('/work2/users/onaka/AKARI/IRC_AllSkyMap_2016/G157m30/G157m30_S_intensity.fits')
# 18 micron data:
fits_display('/work2/users/onaka/AKARI/IRC_AllSkyMap_2016/G157m30/G157m30_L_intensity.fits')
INFO:astropy:Auto-setting vmin to -3.828e+00
INFO:astropy:Auto-setting vmax to  4.931e+00
INFO: Auto-setting vmin to -3.828e+00 [aplpy.core]
INFO: Auto-setting vmax to  4.931e+00 [aplpy.core]
INFO
INFO:astropy:Auto-setting vmin to -6.854e+00
INFO:astropy:Auto-setting vmax to  7.413e+00
: Auto-setting vmin to -6.854e+00 [aplpy.core]
INFO: Auto-setting vmax to  7.413e+00 [aplpy.core]
Out[14]:
<aplpy.core.FITSFigure at 0x2b53207cc6d0>
In [ ]: